Abstract: Policies and technologies to reduce greenhouse gas and climate-active aerosol emissions to limit the magnitude and rate of future climate change hold the potential to benefit health through reductions in ambient fine particulate matter (PM2.5) concentrations. Emissions reductions generally act through (1) improving energy efficiency; (2) increasing combustion efficiency; or (3) increasing use of non-combustion sources. The health co- benefits associated with greenhouse gas emission reductions typically accrue sooner than the risks projected from climate change, which means that mitigation could improve health in the shorter term even as reduced emissions decrease the risks of climate change later in the century. However, these benefits are rarely taken into account when analyzing the costs of specific policies, with the consequence that the estimated costs may be significantly inflated. A challenge to including health co-benefits in assessments of the costs of mitigation is that co-benefits studies use different approaches, with limited consistency in terms of model assumptions, valuation metrics, discounting methods, and uncertainty characterization and propagation. Increasing consistency across modeling studies has the potential to increase the policy relevance and application of co-benefits modeling, potentially helping policy makers maximize mitigation potential while improving health. Meeting goals are to: ? Review the state of the art in modeling the health co-benefits of mitigation policies and technologies, comparing the strengths and weaknesses of different approaches, with the goal of agreeing common methods to enhance comparability across studies; ? Promote collaborations between health and integrated assessment models to facilitate inclusion of health co-benefits into assessments of mitigation policies; and ? Develop a research agenda that identifies priority knowledge gaps, including additional health outcomes to include in co-benefits studies.